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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Because the organogenesis and physiology of the lens are essentially similar in various mammals, an understanding of the etiology and pathogenesis of the formation of cataract in an animal model will enhance our knowledge of cataractogenesis in man. In this review, we summarize the background, etiology, and pathogenesis of cataracts that occur in rodents. The main advantages of using rodent mutants include the well-researched genetics of the animals and the comparative ease of breeding of large litters. Numerous rodent models of congenital and hereditary cataracts have been studied extensively. In mice, the models include the Cts strain, Fraser mouse, lens opacity gene (Lop) strain, Lop-2 and Lop-3 strains, Philly mouse, Nakano mouse, Nop strain, Deer mouse, Emory mouse, Swiss Webster strain, Balb/c-nct/nct mouse, and SAM-R/3 strain. The rat models include BUdR, ICR, Sprague-Dawley, and Wistar rats, the spontaneously hypertensive rat (SHR), the John Rapp inbred strain of Dahl salt-sensitive rat, as well as WBN/Kob, Royal College of Surgeons (RCS), and Brown-Norway rats. Other proposed models for the study of hereditary cataract include the degu and the guinea pig. Because of the ease of making clinical observations in vivo and the subsequent availability of the intact lens for laboratory analyses at different stages of cataract formation, these animals provide excellent models for clinicopathologic correlations, for monitoring of the natural history of the aging process and of metabolic defects, as well as for investigations on the effect of cataract-modulating agents and drugs, including the prospect of gene therapy.
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PMID:Rodent models of congenital and hereditary cataract in man. 195 36

A large sample of lenses obtained from donor eyes spended for cornea transplantation were biomicroscopically screened and a representative subsample of lenses (about 30) exhibiting early opacities were studied at the scanning electron microscopic (SEM) level. Two types of early cortical opacities (Lens Opacities Classification System cortical grade 1a, 1b) could be distinguished biomicroscopically: (1) radial shades, and (2) circular shades. The prevalence of both types is age related, with an earlier occurrence of radial shades than of circular shades. In addition, radial shades proved to occur as single entities in isolation in lenses from people younger than the age of 40, whereas circular shades are only occasionally found in isolation in older lenses. SEM analysis substantiated the existence of the two early forms of opacity. Radial shades were found to consist of restricted parts of a small group of fibers in the deep cortex. These affected parts had membranes with a fine globular aspect and in cross-section proved to be filled with medium to large globular elements. Neighboring fibers and the nonaffected parts of the fibers involved in the radial shades had a normal SEM ultrastructure. Circular shades proved to originate as fractures of a large cohort of fibers in the deep equatorial cortex perpendicular to the course of the fibers. The fractured faces were slightly swollen, but the membranes on both sides of the fracture had a normal ultrastructure. In cross-sections of more advanced circular shades it proved that the broken fibers are filled with globular elements and are opaque. This opacification proved to extend only in one direction: either anteriorly or posteriorly. The results strongly suggest that two distinct early cataractogenic cellular processes are operating in the aging human lens. The possible induction of circular shades by radial shades, as can tentatively be concluded on account of the difference in appearance during aging of circular and radial shades, needs further verification by SEM analysis of more severely affected lenses. The observations corroborate the suggestion by Bron and Brown of the existence of mechanisms within the lens that separate damaged from undamaged fibers (segregation) or separate affected parts from unaffected parts of individual fibers (sealing).
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PMID:Biomicroscopy and scanning electron microscopy of early opacities in the aging human lens. 238 88